This speach is about similarities and dissimilarities in brain changes induced by cannabis, psilocybin and ketamine. It is a fMRI study. Prof. Jiří Horáček, M.D., Ph.D. is a Professor of Psychiatry at the 3rd Faculty of Medicine, Charles University, Prague, Czech Republic. He holds a degree in psychiatry and psychotherapy. He is currently the Deputy Director of the National Institute of Mental Health, Czech Rep.. Prof. Jiří Horáček has been actively involved in 40 scientific research projects. His research activities involve the use of brain imaging (PET, fMRI and qEEG) in the fields of schizophrenia, depression and OCD, psychiatric genetics and the animal modeling of mental disorders. He is both the editor of several books and the author of more than 100 scientific articles. Prof. Jiří Horáček has received several national and international psychiatric awards from the International Pharmaco-EEG Society (Werner Hermann Memorial Award), the Czech Neuropsychopharmacological Society and ECNS-ISNIP. In his productive career he has been awarded the Senior Research Fellow of the Bedfordshire CMHR in associatin with the University of Cambridge. He is also the President of the Czech Neuropsychopharmacological Society (2015-2017).